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What does science tell us about the importance of a good bath to a bird?

The answer: surprisingly little!

A study published in 2009 stated it plainly: “Birds of most species regularly bathe in water, but the function of this behavior is unknown” 1.

This post is about the cool green science of bird baths: what we know and intriguing areas of inquiry for future research.

Rub-a-Dub-Dub, Many Birds in the Tub

Despite the lack of knowledge about the function and importance of baths to birds, we all know that birds (like the rest of us) love having water around for bathing and drinking.

When working with migrant birds in the Yucatan Peninsula, I first began to understand how seriously birds take the business of bathing. We were studying warblers that were typically territorial. These birds frequently engaged in threat postures and even in fights to enforce the boundaries between their exclusive home ranges at our mangrove study sites.

Each evening at dusk, in a special spot in the mangroves where a freshwater spring bubbled up from the ground, numerous American redstarts, northern parulas, magnolia warblers, common yellowthroats and yellow warblers took turns bathing.

One by one, they shared this little oasis before going to roost for the night.

Seeing territorial warblers calmly taking turns for a bath tells us that for a bird, having access to water for bathing is worth checking one’s combative tendencies – at least for a few minutes.

Why Birds Take Baths

So, what’s so important about a bath?

Starlings that take baths may be better able to elude predators. Photo: Flickr user NatJLN under a Creative Commons license.

The number of relevant scientific articles can be counted on one hand. There are very basic descriptions of the mechanics of bird bathing in North American2 and Australian birds3, an experimental examination of wetting and drying of disembodied feathers4, and a recent pair of studies that experimentally deprived captive starlings of bath water 5,1.

Although the functions of bird bathing aren’t clearly known at this point, these studies suggest that bathing plays an important role in feather maintenance.

Feathers are a bird’s lifeline: they insulate, waterproof and, of course, provide the power of flight.

Feathers get replaced once or twice a year. In the interim, they need to be kept in good condition. The sun, feather-munching mites, bacteria and gradual wear take a toll on feathers. A set of year-old flight feathers look like they’ve been through the ringer: they are frayed and dull.

A good bath may keep those precious feathers in the best condition possible for as long as possible.

Two recent studies on captive starlings have progressed our understanding a bit further. In one paper, Brilot and colleagues hypothesized that depriving a bird of a bath would result in more disheveled feathers and translate into poorer flight performance.

They tested a group of freshly-bathed starlings and a group that had been deprived of a bath for three hours prior to the experiment. The starlings deprived of a bath were clumsier when flying through an obstacle course made of vertically-hung strings, bumping into more strings as they flew.

In their second paper on starlings, the research team examined whether the bath-deprived starlings knew they were clumsier. They did this by presenting bathed and unbathed groups of birds with recordings of starling predator alarm calls – and delicious meal worms – at the same time.

The experiment indicated that birds with access to bath water were more willing to let their guard down and feed, despite the recorded call signaling the presence of a predator. The authors suggest that the unbathed birds were more cautious because they were aware that their ability to escape was impaired.

This work tells us that, beyond preserving feathers over the long term, bathing even makes a bird a more agile flier and more adept at escaping predators in the short term.

These studies are helpful, but the function of bathing still eludes us.

How does it make these birds better fliers? Does it help realign the tiny barbs that hold feathers together? Does it help distribute protective oils? Does it improve feather performance in some other way?

This all leaves me wondering about those birds in the Yucatan. Our research was focused on revealing differences in habitat quality among individuals, mainly by measuring the food resources of the birds. We reasoned that more food equaled birds in better condition with a better chance of survival.

But maybe we were ignoring another important aspect of habitat quality – access to bathing water. We see from the starling work that being deprived of a bath could make an unbathed bird easier to catch, so baths might play a role in survival too.

Until we get an answer from science, we will need to rely on common sense and keep those backyard bird baths full.

Preparing Your Backyard Bird Bath

Many of us with bird feeders also have a bird bath to go along with it. Even in the coldest months of the year, I’ve found that birds are eager to take baths.

I recently poured a warm tea kettle of water into my frozen bird bath and there was an instant scrum as the cardinals and white-throated sparrows jockeyed for position around the bath.

Joe Smith, PhD, explores the lives of the birds around us by sharing insights from scientific research. As an ecologist for a New Jersey-based conservation services company, he helps to restore coastal ecosystems and the migratory birds that depend on them. Joe lives in the birding hotspot of Cape May, NJ and has done field research with birds throughout the U.S. and Latin America. He writes about nature in his backyard at www.smithjam.com.
More from Joe

As you’ve described it, I’d say that the experiment demonstrates a higher level of anxiety but that may or may not be from an awareness of increased vulnerability. Bathing may simply reduce stress/anxiety, much like a shower can for a human. A step further, that bathed birds are less clumsy may be because bathing is invigorating and have nothing to do with feather condition. Spose I should try and read the published article.
Re mosquitos: bird baths and other water holders if cleaned out before the mozzies can complete their cycle make great traps to reduce the total mozzie population.

My first thought was that birds have mites and a bath would wash those terrible little biting creatures off, so they can get a good nights sleep. I have chickens and the birds come into their pen to “barrow” some chicken food. They leave mites behind that my chickens get. My girls and roosters hate water on their feathers, but take a dust bath to calm down and reduce the mites. A little bit of fire place ash in the dust/dirt aids in the reduction of their mites.

Why do research on bird bathing. It is a natural thing that they do and to deprive some of the birds from bathing is inhumane. Leave them alone and let them enjoy being birds. Unless I can get a good reason for this research, I hope my donation dollars are not going towards this research.

I would like to know how birds manage to fly at all in northern climes where they have no access to bath water for months on end. When major tributaries like the Hudson River are completely covered with ice, the smaller ponds and puddles favored by birds will surely be frozen as well. How does the starling study explain that?

I would assume that another reason for bathing has to do with nesting. Birds can regulate the amount of humidity on their clutch of eggs by taking a bath. Some birds have specialized breast feathers that absorb water i.e. the Sandgrouse. I would also think it would be refreshen for a bird to bath after taken a turn at sitting on eggs.

[…] dark the robin with the bright yellow beak and showy red breast (the male) took a long bath. Splish, Spash: Why do Birds Take Baths? a post on The Nature Conservancy’s blog attempts to answer the […]

Baths do wonders for feather quality. My wife’s parrot becomes more and more disheveled, the longer it’s been since his latest bath. Flight feathers (wing and tail) fare the worst. A bath restores the feathers almost completely.

I have several bird baths of varying sizes and depths in strategic spots in my yard, and different birds favor different baths. I love watching them bathe, and the pitter patter of their splashing never fails to make me grin. I always thought there were several reasons for bathing:

A flock of finches just used our bird baths. How do birds know where they are? It seems like they tell each other because we get more and more. Titmouses, chickadees, cardinals, blue birds, bluejays, Carolina wrens, and more.

I;ve collection of videos taken from my house. ‘LET THE BIRDS COME TO YOUR HOUSE” is the title of my project. I ‘ ve to make a documentary on the subject “birds bath’ I think your valuable contribution if any as literature on the subject specified .. Sir?

Local murray magpies (small) regularly come to our ceramic bird bath, fluttering around and raising wings, and today in Spring a dove actually sat in the middle of same. More a small bird thing.
Adelaide Australia. Note the bird bath is in a small protected courtyard garden. But they do sense when I watch and clear off.

Nice article! If we are to keep our birdbaths full, we need to fill (two baths) approximately every 2-3 hours in the summer. I live in Metro Detroit. We have limited the birds to having only 3 refills of water each day! There are usually 3-12 birds in each bath at any given moment. Mourning Doves are the last of the day, the circle the baths and face out towards the yard and stay until dusk. I keep a birdbath with a heater in the winter also.

We were puzzled to see small birds bathing in a plastic tray in our UK garden, even though its very cold and there is snow on the ground. Now we understand better why birds need water and that it’s not just for drinking, so we’ll take care that they always have a supply this winter/